Voltage regulator for alternating current lighting system

ABSTRACT

A semi-conductor voltage regulator includes a dual transistor differential amplifier pair adapted so as not to be damaged by reverse voltages during the application of either polarity of alternating current to the associated sensing network. The sensing network includes resistors, the value of which are selected to provide an offset current during one polarity of alternating current with respect to the other polarity. A diode is coupled with the differential amplifier transistor pair in order to protect those devices and the load from high, suddenlyapplied or transient voltages generated externally or by internal switching within the regulator.

United States Patent [1 1 Minks 1 VOLTAGE REGULATOR FOR ALTERNATINGCURRENT LIGHTING SYSTEM [76] Inventor: Floyd M. Minks, Rte. No. 1, Box66,

Kissimmee, Fla. 32741 [22] Filed: Nov. 21, 1973 [21] Appl. No.: 417,773

[58] Field of Search 307/252 N, 252 W; 315/78,

[4 1 Dec. 2, 1975 Primary Examiner-A. D. Pellinen Attorney, Agent, orFirm-Duckworth, Hobby & Allen [57] ABSTRAGT A semLconductor voltageregulator includes a dual transistor differential amplifier pair adaptedso as not to be damaged by reverse voltages during the application ofeither polarity of alternating current to the associated sensingnetwork. The sensing network includes resistors, the value of which areselected to provide an offset .current during one polarity ofalternating current with respect to the other polarity. A diode iscoupled with the differential amplifier transistor pair in order toprotect those devices and the load from high, suddenly-applied ortransient voltages generated externally or by internal switching withinthe regulator.

9 Claims, 3 Drawing Figures [56] References Cited UNITED STATES PATENTS3,241,044 3/1966 Mills 323/22 SC 3,469,177 9/1969 Lorenz...... 323/22 SC3,538,427 11/1970 Oltendorf 323/40 X 3,641,397 2/1972 Elliot ct a1.307/252 W US. Patent Dec. 2, 1975 3,924,154

VOLTAGE REGULATOR FOR ALTERNATING CURRENT LIGHTING SYSTEM The presentinvention relates to AC voltage regulators and more specifically tovoltage regulators such as would be used on snowmobiles or motorcyclesor other small vehicles where the headlamp and taillamp are normallyoperated directly from the coil of an alternator as opposed to thebattery operated systems on most automobiles. Regulators for thispurposeare described for example, in my prior U.S. Pat. No. 3,757,199,3,755,685, and 3,755,709. While these systems have proved both workableand commercially practical, it is the purpose of the present inventionto increase the accuracy and allow adaptation in applications such asfor instance, with low voltage lamps, say typically 6 volt systems whereapplication of the previous art is more difficult. The amplifyingcircuits interposed between the RMS sensitive network and the shuntswitching device in the reference just mentioned generally are limitedto relatively little output and therefore require shunt switchingdevices of high input sensitivity. These circuits typically use an SCRof 3 milliamperes or less maximum gate current to fire, and in somecases, under I milliampere. Circuits of the present invention areusuable with more readily available and higher current SCRs, thepractical gate sensitivity range approaching 10 milliamperes. Also thecalibration of the previously mentioned art is somewhat dependent uponthe characteristics of the alternator supplying the power for thesystem, therefore in some cases, requiring different calibration pointsfor use with different alternators to produce the same regulatedvoltage. Therefore, the further object of this invention is to produce aregulator with minimum sensitivity to the characteristics of thealternator being regulated. In U.S. Pat. No. 3,755,709. note that thegate drive current for the SCR must flow through either R-l or L whichcomprise a portion of the voltage sensing network of the regulator. Thiscurrent therefore reflected into the impedance of this sensing circuitnode produces a voltage drop dependent upon the gate sensitivity of theSCR which varies from unit to unit and with temperature, thus producingunwanted deviation from ideal regulation. Also in that reference, theoutput of the bridge circuit is imposed directly across the base emitterjunction of a transistor. This produces two undesirable effects. First,the well known temperature coefficient of the base emitter junction of abipolar transistor produces a change in regulated voltage withtemperature; secondly, since a finite voltage, say typically half avolt, is required to bias on the base emitter junction, the bridgecircuit does not operate at a true null, so the regulation point isdependent upon the RMS voltage applied as is desirable, but alsosomewhat upon the instantaneous peak applied to the bridge to producesufficient output signal to drive this junction. It is therefore theobject of this invention to overcome both of these limitations. Also inthe previous reference, the power sensitive impedance L is equallyresponsive to the positive and negative portions of the input wave formbecause R-l is a linear resistor. It is another and further object ofpresent invention to make the response of the sensor slighly offset tofavor one polarity of the wave form so as to reduce an instability thatmight otherwise result at the point where the alternator has onlyslightly more output than required by the lamps or other loadsconnected. Another and further object of the present invention is toreduce the requirements, and therefore chance of failure on theamplifying devices typified by the transistor inU.S. Pat. No. 3,755,709.As previously mentioned, considerable output is needed from thebridgecircuit in that case requiring a fairly large voltverse direction, fromexceeding safe levels. For the THE- DRAWING FIG. 1 is a first embodimentof a circuit in accordance with the present invention, utilizing adifferential amplifier therein. v

FIGS. 2 and 3 are alternate embodiments to the embodiment shown in FIG.1, both in accordance with the.

present invention.

The invention will now be described with reference to the accompanyingdrawings, FIGS. 1, 2, and 3, which are circuit diagrams of threeembodiments of the invention. The specific novel circuits described inreference to these three figures may not all be required in any specificapplication or a combination of them may be required in certainapplications. While all of thefigures show a power sensitive impedancein a bridge circuit as the sensing network, various other networks suchas shown in U.S. Pat. No. 3,755,685 could be utilized or indeed entirelydifferent networks such as known in the art. Other and furthermodifications and adaptions .of this circuit should be obvious to thoseskilled in this art. In all figures, similar numbers with primes anddouble primesrepresent components with similar functions. A representsan alternating current source of power such as might be a permanentmagnet alternator on a snowmobile engine. The voltage, waveform, andfrequency of such an alternator varies with the engine speed, preventingthe use of regulation techniques based on a sinusodial supply voltage. Lrepresents the load to which the power or RMS voltage is to 'be.controlled. Again, the typical snowmobile application will bepredominately lights. The other components are within the regulatorassembly. It should be realized that in general the wiring system ofsuch a vehicle is much more complex than the simple parallel connectionof an alternator and a lamp as shown here and would generally involvesuch things as switches for high beam and low beam, brake lightswitches, and other similar wiring. 1 is a capacitor by-passing theregulator lead to ground. In some applications this is necessary toprevent interference with the regulator from externally generated highfrequency transient such as from an ignition system or in other cases toprevent switching transients from regulator components from generatingradio interference which might be picked up on a radio mounted on avehicle. 2 represents a solid state control device shown by the acceptedsymbol for a silicon controlled rectifier. Its current carrying anodeand cathode, terminals are connected directly in parallel with thealternator and load so as the device can act as a shunt regulatorcontrolling the voltage applied to the load when a control signal ofappropriate amplitude and phase is applied to its control or gateterminal. Linear resistors represented by 5, 6, and 12, together withthe non-linear device represented by 13, which may be a tungstenfilament lamp, taken as a network act as a sensor for AC or RMS voltage.These components should be understood together as representing ageneralized network of four terminals with an input fed by voltageproportional to that voltage to be controlled, in this case connecteddirectly across the alternator, and an output voltage or impedance inthis embodiment represented by terminals X and Y which has a discernablecharacteristic change when the input voltage passes through the level atwhich it is desired to be regulated. In this case this network is abridge circuit arranged so that the output voltage phase and amplitudeare controlled by the true RMS value of the applied waveform.Differential amplifiers typical of the arrangement of components 7, 8,and 10 are commonly used in DC power supply art and will therefore notbe described in great detail herein. Direct adaptation to alternatingcurrent circuitry however, presents problems with maintaining theinverse voltages on the junctions within acceptable limits. In the baseemitter junction of a transistor even small reverse currents, producingdissipations well below the dissipation capability of that junction inthe forward direction will cause permanent damage to the transistor.This is generally a progressive phenomenon first noted as a reduction inforward current transfer ratio, particularly at low current levels. Theusual approach is to rectify and filter the portion of the AC poweravailable and use this to supply the transistors, however, this approachis generally too large physically and too expensive for practicalcommercial applications to the type of circuitry being discussed here.Diode 9 connected from the alternator lead B to the emitters of thetransistors is used as a protective device to limit the inverse voltagesacross the base emitter junctions of transistors 8 and 10. When theground point is negative compared to point B, current will flow throughdiode 9 and resistor 7. For normal circuit values voltage drop acrossthe diode, if it is a typical silicon device will be in the range of 0.7volt while supplying current through resistor 7 of less than 100millamperes peak. Also the portion of the current flowing through diode9 may flow in the forward direction through the base emitter junction oftransistor 8 to point X, thence through resistor to ground, thusreducing the peak voltage across resistor 6 to typically 1.4 volts.Current may also flow through diode 9 emitter base junction oftransistor 10 and resistors 11 and 12 to ground. Note, however, withmany commonly available transistors the forward voltage drop of thecollector base junction will be sufficiently low that the predominantcurrent path through resistor 11 will be directly from the collector tothe base of transistor 10,

still talking of course at an instant when the alternator outputconnected to ground is negative. Therefore in the typical case,conduction of current from the collector to the base of transistor 10will limit the voltage on that base to a negative peak of approximately0.7 compared to the alternator output lead B. Thus it is seen that theinverse voltages imposed on the transistor junctions are at all timesheld well below the three to ten volt ratings of most commerciallyavailable transistors and this is true regardless whether these'inversevoltages tend to arise from current through the emitter supply resistor7 or from a voltage differential across the input to this transistorpair represented the points X and Y. If transistors 8 and 10 havesimilar transconductance versus temperature characteristics eitherbecause of selection or because of uniformity within the transistortype, this configuration becomes inherently temperature compensated.This will not be discussed in detail here because it is well understoodand presented in the literature where this type of circuitry is appliedto DC applications. In the same way input offset voltages between theterminals X and Y are, or can be maintained to low levels by eitherselecting a match between these transistors or in the general case byuse of transistors of a type that exhibit relatively little differencein these parameters from unit to unit. This allows use with sensors ornetworks as represented in this case by resistors 5, 6, l2 andnon-linear resistor 13 with much lower outputs and would be possiblewith direct connection of the output, for instance to the base emitterjunction of a transistor as shown in the previously mentioned patents.Several advantages arise from this. Circuitry can be readily adapted to6 volt or even lower voltage lighting systems whereas the performance ofthe previous art tended to degrade rapidly below 12 volts RMS systems.Also the operating point of the device 13 which may be typically atungsten filament lamp can be much more-arbitrarily chosen, therefore,in some cases extending the lifetime of that component. Described inanother way, the use of the dual transistor configuration to replace thesingle transistor in the previous art reduces the component of thesensor output network signal between X and Y which is proportional tothe instantaneous peak voltage on that network. This is because thenormal operating output between points X and Y becomes very nearly zerovoltage instead of the forward bias base emitter voltage of thetransistor where a single transistor is used. Ideally in an AC regulatorunder steady state or slowly changing alternator output conditions theshunt switching or control device represented by 2, typically a siliconcontrolled rectifier, should fire at the same point in each succeedingcycle, that point or phase angle being determined by the difference inthe power available from alternator A and the power required by load L.This exact and consistent phase relationship from cycle to cycle isgenerally obtairied in such applications as motor speed controls or someindustrial heating controls by relatively large and expensive networksof resistors and capacitors. Such techniques again may not be practicalin this type of application because of cost and size limitations andpossibly because of the temperature extremes inherent. The phasing inthe circuit of FIG. 1 between the alternator signal A and the gate driveto SCR 2 is partially determined then by the thermal time constant ofdevice 13 compared to the operating frequency of alternator A andpartially by the phase component of the signal between X and Y aspreviously described. While this technique is simple and reliabledeviation from ideal performance may be sufficient to cause problems insome applications. This might most typically be noted as a flickering inlamp L particularly at the point where the output of alternator A isjust slightly above the power required by lamp L. This typically resultsfrom a cyclic variation in the phase angle of the gating of device 2. Ina typical situation, device 2 fires near the negative peak of voltage atpoint B on one cycle and might not fire at all for the following one,two or three cycles,

and then the process is repeated As was previously described, thevoltage required between points X and Y to drive the dual transistorconfiguration is small compared to that of a single transistor, reducingone major cause of these sub-frequency variations. However, it isdesirable to introduce a signal generally increasing with time from thebeginning to the end of the time period when point B is negative withrespect to ground, this being the time period when device 2 is capableof being turned on. This is done in the following manner: the thermaltime constant of device 13 is not so much longer than the period ofalternator A that there are absolutely no changes in the resistance ofthis device during the cycle. Therefore, if the current passing throughdevice 13 and therefore the power in it is made slightly more responsiveto one polarity of the output of alternator A than the other polarity atemperature variation and therefore an output variation at the frequencyof alternator A can be created. It should be pointed out that thedesired size of this signal is very small compared to the normal signalout of this device. In the circuit of FIG. 1 this is created as follows:when point B is positive with respect to ground, as previouslydescribed, current can flow through diode 9 and emitter base junction ofthe device 10 or directly through the collector base junction of thedevice 10 and through resistor 11. This path effectively by-passes aportion of the current through resistor 12 around device 13. Generally,the value of resistor 11 compared to the normal operating resistance ofdevice 13 can be selected to obtain the optimum ratio betweensensitivity of device 13 to power during the different polarity halfcycles without the impedance of resistor 11 being sufficiently high toeffect the operation of transistor 10 during the period of the cyclewhen it is conducting. In a more general sense the sensor is made to beslightly more responsive to one polarity of the applied AC signal thanto the other and this in conjunction with the appropriately selectedrelationship between the sensor network time constant and the frequencyof the alternator is used to produce a more stable phase relationshipbetween the firing angle of SCR 2 and the alternator A. This techniquecan of course be applied to other than the power sensitive impedance 13or to other methods of sensing its operating condition and amplifyingthe resulting signal, than the methods shown by incorporating it in abridge and using the common emitter to transistor configuration shownhere. Resistor 4 from the gate to the cathode of the switching device 2is necessary with some types of devices to insure high temperaturestability. Other types, however, do not require its use. Resistor 3 isnot always required and would generally not be used unless resistor 4was also used. The purpose of resistor 3 is to provide an alternatesource of gate signal to device 2 which is always present above apredetermined instantaneous voltage from point B to ground. Conditionsunder which this would be desirable would be when alternator A mayincrease its output, such as by rapid acceleration of the engine towhich it is attached, so rapidly that the time constant desirable fordevice 13 for steady operation would not be sufficiently short toprevent a short term high value transient in the RMS voltage applied tothe load. An even worse example of this would be if a loose lead orconnection existed in one of the leads from alternator A to the rest ofthe vehicle. Under such conditions as these, the peak responsivecharacteristics of the network consisting of components 2, 3 and 4 canbe highly desirable, protecting the components of the regulator as wellas the load. In some cases this can be accomplished with sufficientaccuracy with 3 and 4 representing linear resistors, however, evengreater accuracy would be obtained with component 3 representing a zenerdiode or other non-linear device with a known and pre-determined voltagebreakdown characteristic. Protection for the first /2 cycle if point Bis positive is not possible with an SCR, but is generally not necessary.The current through device 3 is controlled only by the instantaneousalternator voltage and is not effected or controlled by the presence orabsence of a signal through the path normally driving the gate of device2, that is, through resistor 7 and transistor 8. This normal paththrough components 7 and 8 for the gate current of device 2 isnotthrough any element of the sensing network in this figure represented bycomponents 5, 6, l2, and 13. Thus the impedance of these elements may beconsiderably higher than in the art shown in US. Pat. No. 3,755,709,thus reducing the restraints on the selection of these components tofulfill their other requirements, and also reducing the error signalsresulting therefrom. If diode 9 is replaced by a diode in series withresistor 7 the transistors are still protected from reverse voltagesarising from current flow through resistor 7. In this case, however, thevarious other impedances in the circuit, specifically 4, 5, 6, 11, 12and 13, must be selected with such magnitude to ensure that the voltagebetween points X and Y does not exceed the junction breakdown capabilityof the devices. Also the forward voltage drop of a diode in series withresistor 7 would subtract from the current available through transistor8 to drive the gate of device 2 which might be significant at lowinstantaneous values of the voltage at point B. There would however bethe advantage that the average power dissipation in resistor 7 would bereduced to 50% or less of the value present in the circuit as shown.

FIG. 2 is a circuit diagram of another embodiment of the invention.Components with similar functions are similarly numbered to FIG. 1 withthe addition of a prime and their functions will not be described again.Semiconductor device 16' shown as symbol commonly known as acomplementary SCR is used as an amplifying and switching device. In morerecent manufacturers literature these devices are also frequently calledprogramable unijunction transistors. In the general case they can bemade up of two inter-connected bipolar transistors in the configurationgenerally shown in the literature as being the equivalent of a fourlayer switching device. ,This device serves as the amplification of therelatively low level signal available between points X and Y to producethe required signal to drive the gate of device 2'. The path of the gatecurrent is predominately through the resistor 5' and device 16', howeverif 16 is a switching device as shown, and thus stays on once its gate orinput signal level reaches a predetermined level the errors, describedas being eliminated in FIG. 1 by the gate current path being throughdevice 7 rather than through the bridge, do not exist in the embodimentof FIG. 2. However, if device 16' is replaced by a bipolar transistor,the impedances of devices 5, 6, l2 and 13' would have to be low enoughto supply the resulting base and emitter currents without resulting inunacceptably large errors. Diode l5 and resistor 14' perform a dualfunction. The first function is analgous to the decrease of the portionof current through 13 during the time B is positive by bypassing aportion of it through transistor 10 and resistor 11. In the case of FIG.2 the current through 13 is increased during the opposite half cycle orwhen point B is negative with respect to ground by the path throughdiode 15 and resistor 14' which are parallel with the main current paththrough 12. The second function is to cancel out the offset voltage andto a large extent the temperature co-efficient of the input of device16, thus to a somewhat more limited extent device 16' serves a functionsimilar to transistor 8 in FIG. 1 and device 15 serves a functionsimilar to transistor 10 in FIG. 1.

FIG. 3 is a circuit diagram of a portion of a similar regulator, similarnumbers and double primes being used to denote components of similarfunctions. In this embodiment resistor 18" serves the dual purpose ofboth resistors 3 and 5 in FIG. 1 and resistor 19" serves the dualpurpose of both resistors 4 and 6 of FIG. 1. Device 16, shown as asilicon controlled rectifier is a switching device gated on by apositive signal on the gate, and thus allowing conduction from the anodeto cathode. The analogy of devices 14 and 15' to those shown as 14" and15" is direct, in that they serve both to unbalance the current flowfrom one half of the cycle to the next in device 13' and also to buckout and temperature compensate for the gate to cathode voltage requiredto turn on device 16". Other modifications, combinations, or deletionsof some of the functions described in these figures will be obvious tothose skilled in the art in adapting this teaching to the requirementsof a specific application, and all such being considered to fall withinthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:

*1. In a lighting system for use with an AC power producing source thefrequency voltage, amplitude and waveform of which vary from time totime and having lighting means connected to be energized by the AC powersupplied from said source: a voltage sensitive network having terminalsconnected to be energized by the waveform of said source and havingoutput terminals producing a signal dependent upon the true RMS voltagevalue of said source; control means connected to control the flow of ACpower from said source to said lighting means and having an input means;two amplifying means each having an input terminal, an output terminal,and a common input-output terminal, the common input-output terminals ofsaid amplifying means being connected together, the output terminal ofone amplifying means supplying power to said input terminal of saidcontrol means; said input terminals of said two amplifying means beingconnected to said output terminals of said true RMS voltage sensitivenetwork to regulate the AC power supplied by said source to saidlighting means; impedance means for preventing destructive voltages andcurrents from appearing between said input terminals and said commoninputoutput terminals of said amplifying means for either polarity ofthe waveform applied to said network to prevent the true RMS voltagesupplied from said source to said lighting means from rising above apreselected value; and means to make said network slightly moresensitive to one polarity portion of the waveform of said source than tothe other polarity portion.

2. A system for supplying AC power from a source to a lighting means,comprising: a control means for varying the flow of AC power from saidsource to said lighting means; a network sensitive to a true RMS voltageapplied thereto and having an output, said network energized by thewaveform of said source; means to make said network slightly moresensitive to one polarity portion of the waveform of said source than tothe other polarity portion; means connecting the output of said networkto said control means to regulate the AC power supplied by said sourceto said lighting means.

3. An AC vehicular power system including an engine-driven alternatorand a lighting load to be energized therefrom; a control means with aninput means capable of limiting the AC voltage supplied from saidalternator to said load in response to a signal at its input means; afirst true RMS voltage sensitive network energized by the waveform ofsaid alternator and having a time constant longer than the period of thevoltage produced by said alternator and having an output; a secondvoltage sensitive network having a time constant shorter than the periodof the voltage produced by said alternator and therefore primarilysensitive to peak voltages, and having an output; means connecting saidoutputs of both said networks to the input of said control means toprevent the voltage of said system from exceeding predetermined voltagesfor longer than predetermined times; and means to make said networkslightly more sensitive to one polarity portion of the waveform of saidalternator than to the other polarity portion.

4. A system for supplying AC power from an enginedriven alternatorsource, the voltage, frequency, and

waveform of which vary from time to time to a lamp load; including atrue RMS regulator; said regulator containing a semi-conductor switchingmeans connected to control the flow of power from said source to saidload and having a gate terminal means; a true RMS voltage sensitivenetwork energized by the waveform of said alternator source and havingterminals connected to said source and having output terminals; acontrol signal path for connecting said output of said network to saidgate, said path containing a semiconductor junction biased and connectedso that the forward voltage drop thereof cancels with a similar dropinherent in other components of said regulator at the time when a gatesignal is required to produce a stable RMS voltage to said load, wherebysaid regulator regulates the AC power supplied by said alternator sourceto said lamp load; and means for making said network slightly moresensitive to one polarity portion of the waveform of said alternatorsource than to the other polarity portion.

5. In a lighting system for use with an AC power producing source thefrequency voltage, amplitude and waveform of which vary from time totime and having lighting means connected to be energized by the AC powersupplied from said source: a true RMS voltage sensitive network havingterminals connected to be energized by the waveform of said source andhaving output terminals producing a signal dependent upon the RMS valueof said source; control means connected to control the flow of powerfrom said source to said lighting means and having an input means; twoamplifying means each having an input terminal, an output terminal, anda common input-output terminal, the common input-output terminals ofsaid amplifying means being connected together, the output terminal ofone amplifying means supplying power to said input terminal of saidcontrol means; said input terminals of said amplifying means beingconnected to said output terminals of said true RMS voltage sensitivenetwork; impedance means to prevent destructive voltages and currentsfrom appearing between said input terminals and said common input-outputterminals of said amplifying means for either polarity of the waveformapplied to said network to prevent the true RMS voltage supplied fromsaid source to said lighting means from rising above a preselectedvalue, to thereby regulate the AC power supplied by said source of saidlighting means; and means for making said network slightly moresensitive to one polarity portion of the waveform of said

1. In a lighting system for use with an AC power producing source thefrequency voltage, amplitude and waveform of which vary from time totime and having lighting means connected to be energized by the AC powersupplied from said source: a voltage sensitive network having terminalsconnected to be energized by the waveform of said source and havingoutput terminals producing a signal dependent upon the true RMS voltagevalue of said source; control means connected to control the flow of ACpower from said source to said lighting means and having an input means;two amplifying means each having an input terminal, an output terminal,and a common input-output terminal, the common input-output terminals ofsaid amplifying means being connected together, the output terminal ofone amplifying means supplying power to said input terminal of saidcontrol means; said input terminals of said two amplifying means beingconnected to said output terminals of said true RMS voltage sensitivenetwork to regulate the AC power supplied by said source to saidlighting means; impedance means for preventing destructive voltages andcurrents from appearing between said input terminals and said commoninput-output terminals of said amplifying means for either polarity ofthe waveform applied to said network to prevent the true RMS voltagesupplied from said source to said lighting means from rising above apreselected value; and means to make said network slightly moresensitive to one polarity portion of the waveform of said source than tothe other polarity portion.
 2. A system for supplying AC power from asource to a lighting means, comprising: a control means for varying theflow of AC power from said source to said lighting means; a networksensitive to a true RMS voltage applied thereto and having an output,said network energized by the waveform of said source; means to makesaid network slightly more sensitive to one polarity portion of thewaveform of said source than to the other polarity portion; meansconnecting the output of said network to said control means to regulatethe AC power supplied by said source to said lighting means.
 3. An ACvehicular power system including an engine-driven alternator and alighting load to be energized therefrom; a control means with an inputmeans capable of limiting the AC voltage supplied from said alternatorto said load in response to a signal at its input means; a first trueRMS voltage sensitive network energized by the waveform of saidalternator and having a time constant longer than the period of thevoltage produced by said alternator and having an output; a secondvoltage sensitive network having a time constant shorter than the periodof the voltage produced by said alternator and therefore primarilysensitive to peak voltages, and having an outPut; means connecting saidoutputs of both said networks to the input of said control means toprevent the voltage of said system from exceeding predetermined voltagesfor longer than predetermined times; and means to make said networkslightly more sensitive to one polarity portion of the waveform of saidalternator than to the other polarity portion.
 4. A system for supplyingAC power from an engine-driven alternator source, the voltage,frequency, and waveform of which vary from time to time to a lamp load;including a true RMS regulator; said regulator containing asemi-conductor switching means connected to control the flow of powerfrom said source to said load and having a gate terminal means; a trueRMS voltage sensitive network energized by the waveform of saidalternator source and having terminals connected to said source andhaving output terminals; a control signal path for connecting saidoutput of said network to said gate, said path containing asemiconductor junction biased and connected so that the forward voltagedrop thereof cancels with a similar drop inherent in other components ofsaid regulator at the time when a gate signal is required to produce astable RMS voltage to said load, whereby said regulator regulates the ACpower supplied by said alternator source to said lamp load; and meansfor making said network slightly more sensitive to one polarity portionof the waveform of said alternator source than to the other polarityportion.
 5. In a lighting system for use with an AC power producingsource the frequency voltage, amplitude and waveform of which vary fromtime to time and having lighting means connected to be energized by theAC power supplied from said source: a true RMS voltage sensitive networkhaving terminals connected to be energized by the waveform of saidsource and having output terminals producing a signal dependent upon theRMS value of said source; control means connected to control the flow ofpower from said source to said lighting means and having an input means;two amplifying means each having an input terminal, an output terminal,and a common input-output terminal, the common input-output terminals ofsaid amplifying means being connected together, the output terminal ofone amplifying means supplying power to said input terminal of saidcontrol means; said input terminals of said amplifying means beingconnected to said output terminals of said true RMS voltage sensitivenetwork; impedance means to prevent destructive voltages and currentsfrom appearing between said input terminals and said common input-outputterminals of said amplifying means for either polarity of the waveformapplied to said network to prevent the true RMS voltage supplied fromsaid source to said lighting means from rising above a preselectedvalue, to thereby regulate the AC power supplied by said source of saidlighting means; and means for making said network slightly moresensitive to one polarity portion of the waveform of said source than tothe other polarity portion.
 6. The system of claim 5 wherein said sourceis an alternator attached to an engine of a vehicle.
 7. The system ofclaim 6 wherein said amplifying means are transistors with theiremitters connected together.
 8. The system of claim 6 wherein saidnetwork contains a lamp with an impedance which varies with the powerapplied thereto.
 9. The system of claim 8 wherein said source is analternator attached to an engine of a vehicle and said lighting meansare lamps associated with said vehicle.